It has been found possible to prepare antisera with antilymphokine activity. Such antisera can serve as immunoadsorbents to remove migration inhibition factor (MIF), macrophage chemotactic factor (MCF) and skin reactive factor (SRF) activity from active supernatants. They can also suppress delayed hypersensitivity when administered in vivo. Current experiments involve the further purification of lymphokines by adsorption and separation techniques, in order to obtain better starting materials for immunization. Antisera to be prepared will be used to block various manifestations of cell-mediated immunity such as the macrophage disappearance reaction and the transfer reaction.